Implement control means for tractor operated agricultural implements



April 19, 1966 G. E. SMELCER 3,246,700

IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED AGRICULTURAL IMPLEMENTS 3Sheets-Sheet 1 Filed July 24 1963 Inw/enzok Zen ELSmeZceI' 629 J Aprll19, 1966 s c 3,246,700

IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED AGRICULTURAL IMPLEMENTSFiled July 24, 1963 5 Sheets-Sheet 2 clay a k A a: Q

M Inventor Zen E SmeZcer G. E. SMELCER ENI CONTROL MEANS FOR TRACTORApril 19, 1966 IMPLEM OPERATED AGRICULTURAL IMPLEMENTS 5 Sheets-Sheet 5Filed July 24 1965 ,Ziflf'nzofl' Glen Z SmZcer (By I f A Ma NZ E UnitedStates Patent IMPLEMENT CONTROL MEANS FOR TRACTOR OPERATED AGRICULTURALIMPLEMENTS Glen 1E. Smelcer, Hinsdale, Ill., assignor to InternationalHarvester Company, Chicago, Ill., a corporation of New Jersey Filed July24, 1963, Ser. No. 297,296 17 Claims. (Cl. 172-7) This invention relatesto implement control systems for tractor operated implements, but moreparticularly to improvements in implement depth control mechanismsemployed therewith.

Implement depth control mechanisms for tractors operating agriculturalimplements are well known and, heretofore, have been offered in a widevariety of arrangements of apparatus and assemblies. Usually the controlmeans in a mechanism of this character is adapted to respond tovariations in the draft of an attached implement and attendant suchaccompanying change in draft to thereafter effect an adjustment in theoperative relation of the implement to the soil. To accomplish this thesystem was designed to initially sense and then respond to variations inimplement draft, resulting generally from a change in the soilcharacteristics in the immediate area of the implement in the ground, byeffecting a raising or lowering of the implement as necessary tomaintain it at a constant draft relative to the soil being worked.Heretofore such variations in draft on the implement have been sensed bymechanisms utilizing resilient means, usually in the form of springsassociated with either of the links of the implement-attaching hitchmechanism, that were reactive for resisting compressive and tensiveforces induced in the links by such draft changes and which reactionsthereafter resulted in transmission via suitable linkage means of asignal to an actuator for raising and lowering the implement to conformwith the changing draft demands.

In most of the prior mechanisms the linkage elements and particularlythe pivotal mounting connections thereof were exposed to very severedirt accumulation conditions which ultimately caused either a freeze-upof one or more of these connections or a fracture of some of theelements resulting from excess loads imposed by such conditions. Some ofthese linkage mechanisms also utilized adjustable means in the form of aturn-buckle assembly in the links and these likewise provedunsatisfactory because of a tendency to break or fracture. The aboveconditions also frequently caused the pivotal connections that carriedthe sensing linkage to become heavily loaded or to freeze-up or bind andthus considerably reduced the sensitivity of the sensing mechanism sothat the signal finally transmitted to the actuator did not properlyreflect the degree or magnitude of the draft change on the implement.Additionally, because of the difficulties of economically producingconsistently good springs with identical reactive characteristics thatwere large enough to take the draft load, and because of the erraticfrictional characteristics of springs, as well as of the linkages whenencumbered by the above accumulation hindrances, plus the space factorcomplications encountered on many conventional tractors, the priorsolely spring type mechanisms have not been altogether satisfactory. Animportant feature of the present invention, therefore, is directed toproviding an implement depth control mechanism that avoids theaforementioned earlier drawbacks inherent in prior mechanisms of thischaracter, and concomitant therewith providing a more consistentlyreliable and sensitive mechanism.

The principle object of the present invention, therefore, is to providenew, improved and highly reliable Patented Apr. 19, 1966 draft sensingmeans for tractor vehicle-connected groundworking implements.

A general object is to provide an implement depth control mechanismwherein a draft sensing load creates a pressure differential in ahydraulic circuit which the mechanism effectively measures andsubsequently converts a resultant measurement into a signal thatoperates actuator means to adjust the depth of the implement in theground according to the draft load demands being sensed by themechanism.

Another object is to provide draft-sensing means wherein hydrauliccylinder and piston means incorporated in a hitch linkage mechanismemployed for connecting an agricultural implement to a tractor vehicleare operative, responsive to variations in draft loads on the implement,

for actuating the vehicles power lift means to effect a raising orlowering of the implement to conform with such changing draft demands,and wherein fluid makeup means are provided to maintain an adequatesupply of fluid at all times during operation in the hydraulic circuitembracing said linkage mounted cylinder.

A further object is to provide for tractor-operated agriculturalimplements, a novel implement control mechanism embodying a hydraulicdraft-sensing means that is also operative to provide tilt adjustmentand control for the implements operated thereby, and which, because ofthe selfcontained nature thereof additionally may be readily applied toand utilized with conventional tractor vehicles with a minimum ofmodification of the vehicle.

A still further object is the provision of a new and improved implementdepth control mechanism embodying hydraulic draft-sensing means, andincluding therewith manually adjustable means for modifying thesensitivity of response of said mechanism to variations in draft loadsbeing sensed by said mechanism.

An important object is to provide an improved draftsensing mechanismwherein a hydraulic cylinder and piston, incorporated in and adapted tofunction as a portion of the linkage, of a hitch linkage mechanismemployed for connecting an agricultural implement to a tractor, areoperative for transmitting sensing signals to actuate a power liftmechanism associated with the tractor and which signals reflectattendant pressure diffen.

entials created between opposite ends of said hydraulic cylinder as aresult of variations in the draft loads imposed on an associatedimplement.

A more specific object of the present invention is to provide implementcontrol apparatus for tractorconnected agricultural implements whereinsaid apparatus includes hydraulic means that senses variations in draftloads on an attached implement and thereafter transmits actuatingsignals to a power lift means for adjusting the depth of the implementin the ground attendant said. draft variations, and which apparatusadditionally includes manually adjustable means adaptable for overridingthe signals of the hydraulic draft sensing means and incident theretolimiting the ability of said sensing means to control the operation ofthe power lift for adjusting the depth of the implement in the ground.

The foregoing and other objects and features of the invention willbecome apparent as the disclosure is more fully made in the followingdetailed description of a preferred embodiment of the invention asillustrated in the accompanying sheets of drawings in which:

FIGURE 1 is a fragmentary and generally diagrammatic view, partially insection, of a tractor equipped with an implement depth control systemembodying the features of the invention;

FIGURE 2 is a generally schematic view, with portions thereof insection, showing the components embodied in the proposed implementcontrol system, and

including illustrated details of the means provided for adjusting thesensitivity of response of the draft sensing apparatus portion thereof;

FIGURE 3 is a vertical sectional view taken generally along the line 33of FIGURE 2;

FIGURE 4 is a fragmentary horizontal sectional view taken generallyalong the line 44 of FIGURE 2;

FIGURE 5 is a fragmentary horizontal sectional view taken generallyalong the line 55 of FIGURE 2;

FIGURE 6 is a view generally similar to FIGURE 1 but showing a modifiedarrangement of the application of the invention; and

FIGURE 7 is a fragmentary plan view of the modified arrangement shown inFIGURE 6.

Referring now to the drawings, it will be noted that the proposedimplement control arrangement has been shown as applied to and utilizedwith a generally conventional type of tractor vehicle which vehicle isdesignated in its entirety by the reference numeral 10. The rear axleand differential housing frame portion 11 thereof, in this applicationof the device, has a pair of transversely spaced lower draft links 12(only one of which appears in the drawings) universally pivoted theretoat 13, for movement, principally, in a vertical plane, and about axeslocated below the axis of the rear axle of the ehicle. A third or upperor top draft link 14 is pivotally connected through the universal pivot15 and bracket 16 to the upper rear portion of housing frame 11. Thelower and upper links 12, 14 extend rear-wardly from the tractor andconstitute one form of what is generally termed an implement attachinghitch or hitch linkage mechanism. At their outer ends the links areadapted for connection, respectively, with upper and lower portions of avertically extending mast member 17 that may constitute a portion of animplement frame 18. The attached earth-working implement depicted hereinis a plow and the frame 18 has extending downwardly therefrom abeam-like member 19 which supports the plow bottom indicated generallyby the numeral 20.

The lower or sometimes called draft links 12 are arranged to be movedvertically usually by suitable power means which, as illustrated,comprises a pair (only one of which appears in the drawings) of liftarms 21 constrained for rotative movement with and secured one each toopposite ends of a rockshaft 22 and each of which arms, in turn, isconnected by a drop or lift link 23 with a respective one of said draftlinks. The rockshaft 22 which extends transversely of the housing frame11 has securedly affixed thereto a crank arm 24 through which saidrockshaft is rocked to lift or lower the arms 21 by a hydraulic motorthat includes a cylinder 25 and piston 26, with said piston and crankarm 24 being coupled by the connecting rod 27. Pressure fluid issupplied to the lift cylinder 25 from a suitable pump, such as indicatedat 28, which, in turn, may be connected by conduits 29 and 30 with theflow of fluid to and from said cylinder controlled by an actuatorcontrol valve indicated generally at 31.

The pump 28 may be mounted within the housing frame 11 and a reservoir30a may be fashioned as an interior compartment or chamber area formedas part of a housing embracing the hydraulic lift cylinder and theactuator valve therefor, as is well understood, hence, it is believed nofurther structural details thereof need be illustrated herein. Actuatorcontrol valve 31, which may be of conventional or well knownconstruction, preferably, but of the type disclosed in US. Patent No.2,716,966, issued September 6, 1955, to Clarence A. Hubert and Joseph F.Ziskal, and is operative selectively to permit delivery of fluid underpressure through a passage to one end of the lift cylinder whilesimultaneously opening another passage for escape of fluid to thereservoir from the opposite end of said cylinder in order to lift thelower draft links 12, and vice versa in order to lower said draft links,or to provide a neutral position wherein the passages to both ends ofsaid cylinder are blocked and the associated circuit is closed.

Now, in accordance with the more specific teachings of the invention,according to one preferred embodiment as illustrated herein, the upperor top draft link 14 is fashioned with a forward link portion 14apivotally mounted at 15 on the bracket 16 in turn suitably affixed tohousing 11, and with its opposite end fixedly secured to the casing ofan auxiliary hydraulic cylinder 32, while a rear link portion 14bpivotally connected at one end thereof to the upper end of mast 17 hasits opposite end connected to a piston 33 slidably operative within thecylinder 32. The rear link portion 14b thus functions, in effect, as aconnecting rod for piston 33. Suitable sealing means, such as the ringsshown at 34, may

be provided in one end of cylinder 32 for cooperation with linkconnecting rod 14b, While, preferably, highpressure flexible hoseconduits 35, 3-6 are connected by suitable fittings 35a, 36a torespective ends of the upper link or auxiliary cylinder 32. The oppositeends of said flexible conduits are connected to suitable fittings suchas 35b, 3611 respectively, which, in turn, are connected by conduits 37,33 to opposite end portions of a casing or housing 39 of a draftsignaling control valve unit designated generally by the referencenumeral 40.

Valve housing 3% is fashioned with a bore 41 extending longitudinallytherethrough that slidably accommodates a relatively small-diameteredpiston 42 there within. One end or face of said piston has suitableaffixed thereto and projecting therefrom guide rod 43, which extendsthrough an aperture 44 in an end wall of valve housing 39 and has formedon the outwardly projecting end thereof an enlarged head or upset endportion 45 while a spring 46 coiled around said guide rod is abuttinglypositioned between the head 45 and the proximate end wall of said valvehousing. Suitable sealing means such as the rings 4-7 may be provided torestrict fluid flow along the guide rod 43 as is well understood. Theopposite end or face of piston 42 has suitably atfixed thereto andprojecting therefrom a plunger member 48 which extends through anaperture 49 in an opposite end wall of said valve housing and hasprovided thereon proximate the outwardly projecting end portion thereofan abutment head or collar 50, while a coiled spring 51 seated on saidcollar and positioned over said plunger is compressibly reactive againstthe latter collar and the proximate end wall of housing 39. Suitablesealing means such as the rings 52 may be provided to limit fluidleakage axially along the plunger member 43. Extending upwardly from oneside of valve casing 3-9 is a pedestal-like portion or projection 53 anda plate-like support member 54 is removably secured to the outer end ofsaid projection by suitable securing means such as the cap screwsindicated at 55. Securedly positioned on the support member 54, by anysuitable means such as the bolts 56, is a bypass valve, operative topermit tilt adjustment of the implement and indicated generally at 57,which comprises a cylinder-like housing 58 with a bore 59 extendinglongitudinally therethrough and having oppositely disposed ports 60, 61,connected respectively, by conduits 62, 63 for bypass or fluidcommunication with fittings 35b, 36b, and a piston 64 slidably disposedin said bore with a plunger rod 65 aflixed to and extending upwardlyfrom one end of said latter piston. A radial aperture 66 extendingthrough piston 64 is provided for a purpose which will presently befurther explained. A cover plate 67, with an opening 68 therethrough toaccommodate plunger rod 65, may be suitably secured as by the bolts 69to the upper end of cylinder housing 58, and a sealing ring 70 may beprovided in said cover plate opening to restrict fluid leakage axiallyalong said plunger rod. A coil spring 71 encircling plunger 65 isseatably positioned between the cover plate 67 and a stop collar orwasher 72 positioned on said plunger and constrained, against axialmovement in one direction, by a pin or cotter key such as 73 suit-' ablysecured in said plunger. The spring 71 is positionably dimensioned andstressed to normally urge piston 64 upwardly so that the aperture 66therein is not in registering alignment with the oppositely disposedport openings 60 and 61 whereby the free flow of fluid between conduits62 and 63 is restricted.

A shell-like housing or support structure indicated in its entirety bythe reference numeral 75, may be fashioned to include an outer perimeterwall 76, an inner closure wall 77 to which said outer wall is affixed,and a plurality of lugs or brackets 78 adapted to receive fastening boltmeans 79 whereby said structure may be mounted on a side wall portion ofthe vehicle housing frame 11. Said structure may, if desired, beprovided as a container-like support for components of the proposedmechanism and a suitable cover plate (not shown) provided for coveringthe contents so as to protect them against excess exposure to dirt anddebris. Suitable conventional mounting means, such as the brackets 40aand fastening bolt means indicated at 4%, may be provided for mountingthe valve 40 and its associated components within said containerstructure, so that said structure long with its components may be addedto the vehicle as a unit or package-like assembly.

The plunger rod 65 extends through an aperture 74 in the upper wallportion 76, of support structure 75, and a suitable sealing andlubricating gland or bushing such as indicated at 80 may be providedthereof as is well understood for such uses. The outwardly projectingend of plunger rod 65 engages a manually operable control or handlemember 81 pivotally mounted at 82 on a bracket 83 supportably carried byand suitably affixed to the upper wall portion 76 of said supportstructure. The pivotal connection 02 may include any well-known frictionor detent means (not shown) suitable for resisting movement of controlhandle 81 out of a preselected position except when manually motivatedout of such position. Since such frictional and detent means areconventional and so well lcnown for similar purposes, it was felt a fulldescription of the structural details of a specific such means hereinwas unnecessary.

It will be appreciated, of course, that the by-pass valve unit 57 couldbe fashioned as an integral part of the housing 39 without deviatingfrom any of the inventive concepts hereof.

The outwardly projecting end of plunger member 4 8, of signalling valve40, is fashioned with a recess or cutaway area 84 (FIG. 5) and has astud or pin 85 mounted thereon which extends into said recessed area andpivotally supports a roller 06 retained on said pin by suitable "meanssuch as the cotter key or pin 87. Spaced axially outwardly from saidstud and securedly afiixed to plunger member 48 is a large-headed pin orstud 88, the head of which also extends into said cut-away area. Theroller 86 and pin 88 as thus disposed serve as a cam follower and guideor man operating means, as will subsequently be more fully understood.

A generally wedge-shaped plate-like cam member 89 with opposite edgescontoured to provide cam profiles substantially as illustrated, has anoverturned edge portion 90 providing a track that is dimensioned forpositioning between the cam engaging roller 86 and guide pin 88 wherebymovements of plunger 48 and cam 89 may be operatively coordinated in apositive cam and follower relationship. The cam-plate member 89 isfixedly secured to a vertically positioned support member 91 whoseopposite ends have afiixed thereto and extending transversely thereofupper and lower roller carrying brackets 92, 92a, respectively. Each ofsaid roller carrying brackets has suitably supported thereon a pair ofspaced-apart identical spindles or studs, such as indicated by thereference numeral 93, which, in turn, journals a respective rollermember 94. An enlarged head or upset portion such as 94a suitablyprovided on the free end of each spindle serves to retain a respectiveroller member thereon.

A cam member support frame, indicated generally at 95 (FIGURE 3),comprises an outer generally C-shaped member 96 and a smaller oppositelyfacing generally D- shaped inner member 97 (with one side thereof open)positioned therewithin, and afiixed thereto by any suitable means suchas the welds indicated at 98, with said members disposed so as toprovide upper and lower tracks 99, 100 each of which slidablyaccommodates a set of two rollers 9-1. A support frame mounting andguide rod 101 has one end thereof suitably secured to said cam supportframe for movement therewith while an opposite or upper end portion ofsaid rod projects through an aperture 102 in upper wall portion 76, ofhousing structure 75, and a suitable sealing and lubricating gland orbushing such as indicated at 103 may be provided thereat as is wellunderstood. The outwardly projecting end of guide rod 101 has alarge-headed pin or stud 104 therein that serves as a cam follower andis positioned so that the head thereof extends into a cam guide track105 fashioned in an arm of a manually operable control member or handle107, in turn, pivotally mounted at 108 on the bracket 83. Cam guidetrack 105 may be [contoured to provide a desired position relation forsensitivity lever 107 and, preferably, will be fashioned as a smoothcurve except for detent notches 106 which serve to locate and maintainthe No Effect zone of cam 89 in alignment with roller 117. It isunderstood, of course, that suitable friction means (not shown) or othersuitable means for fixedly positioning the adjusted vertical locationsof cam track 105 will be provided to normally maintain said controlmember in any rotatively selected position, as is well understood.

The opposite or forwardly facing end edge of cam member 89 has a loweredge portion thereof overturned to provide an inclined cam track 109,while disposed above said latter track is another track, indicatedgenerally at 110 and designated as the draft control operating rangeportion or area of the mechanism, that is formed between the divergingridge or rib members 111, 112 which, in turn, extend outwardly from theface of cam plate 89. Said ridges or ribs may be formed integral withsaid cam plate or separately fashioned and suitably secured to said cammember, as is well understood, without deviating from any teachings ofthe inventive concept hereof. As shown, the track 110 somewhat generallyconforms in camming configuration, although it is not limited thereto,to the track profile provided by end edge portion 90, but it will benoted that the side walls of track 110 diverge so that the lower portionof the track is wider than the upper portion thereof for a reason whichwill presently become apparent. An actuator control rod 113 slidablymounted in an aperture 114 in perimeter wall 76 has one end thereofcut-away or recessed at 115 and a stud or pin 116 mounted thereonextends into said recessed area and pivotally supports a roller 117suitably retained thereon. The roller 117, in turn, is positionablebetween the ridges 111, 112 and, under certain circumstances, adaptedfor contacting engagement with one or the other of said ridges or, withboth of said ridges simultaneously, while at other times with cam track109, and as thus engaged may be made to follow with varying degrees ofcontrol, the movements of said cam member; while at still other times,no engagement occurs with either of said tracks. A boss 118 provided onwall 76 adjacent aperture 114 includes an extension of said aperture forslidably accommodating the rod 113, and a threaded opening 119 in saidboss receives a bearing shoe and a spring 121 held in place by a setscrew 122. The spring 121 urges bearing shoe into frictional engagementwith the rod 113 while the set screw 122 is adjustable to vary thedegree of such frictional engagement, all for purposes which willpresently be readily understood.

The actuator control valve 31 which may be conventional in structure,preferably, is of the type disclosed in the noted US. Patent No.2,716,966 and wherein, as illustrated in the present invention, the liftcylinder 25 and the actuator control valve 31 are disposed in closeproximity to one another in a casing-like structure such as isrepresented herein by the reference numeral 130. Since the operation ofthe control valve and lift cylinder of the present invention issubstantially identical to that disclosed in the above reference US.patent no further elaboration of the structural details thereof need beincluded herein. In the instant invention the actuator control rod 113,which constitutes a part of the signal input means to the actuatorcontrol valve, is normally directly operative responsive to movements ofthe cam member 89 instead of the operators control handle as is the casein said patent structure, otherwise the functioning of the twostructures is identical.

It will be apparent to those skilled in the art that an actuator controlvalve, such as indicated at 31, of the type disclosed in the previouslyreferenced US. Patent No. 2,716,966 is readily adaptable to provide foradmission of fluid into only one end of the lift cylinder in order toraise the implement, while depending upon the weight of the implement toeffect the lowering thereof, without deviating from any of thefundamental teachings of the present invention. In such event, it willbe understood, certain modifications would also he made in the cammember 89 as presently illustrated in order to coordinate the movementsthereof with the operation of valve 31, all of which is well within thepurview and bounds of the present invention.

The opposite or outwardly extending end of rod 113 is connected to ahead 123 which is pivotally mounted at 124 on a walking beam link member125 proximate one end of said link. The opposite end of said walkingbeam link is pivotally connected at 126 to a bracket 127 constrained formovement with the lift cylinder connecting rod 27. Intermediate the endsthereof the walking beam link 127 is pivotally connected at 128 to theoutwardly projecting end of the control element spool or plunger 129 ofthe actuator control valve 31.

A pressure relief and bleed valve, indicated in its entirety at 131, isconnected by conduit 132 to a port 133 opening into bore 41 while theopposite end of said valve communicates by conduit 134 with a hydraulicfluid supply reservoir indicated herein at 30a in housing 130. It willbe appreciated, of course, that any other suitable fluid supplyreservoir on the vehicle could be used for this purpose. Relief valve131, which is generally conventional in structure, includes a ballmember 135 that engages a valve seat 136 and is urged thereagainst by aspring 136a, which spring is stressed so as to constantly permit a smallamount of fluid from bore 41 to bleed past the seat 136 under normaloperating conditions, but will permit full flow exhaust into thereservoir when excess pressure occurs in the latter bore as is wellunderstood.

A combination fluid make-up and surge restricting I valve means,indicated generally at 137, communicates by way of a port passage 138opening into bore 41 and by way of conduit 139 with the pressure side ofpump 28. A casing 140 having a bore 141 therein accommodates a ball 142which may engage either one or the other of oppositely facing valveseats 143, 144 fashioned therewithin, and a plunger 145 has one endthereof adapted to engage said ball while the opposite end of theplunger is aflixed to a cruciform-shaped spider 146 having a small guideplunger 147 on the opposite side thereof. A spring 148 positioned aroundplunger 147 seats against spider 146 and one end of casing 140, while anaperture in said casing is aligned and coterminous with port opening orpassage 138. Suitable means (not shown) will, of course, be provided foraffixing the make-up valve 137 to the draft signalling valve 40 whenthey are separately fashioned. It will be appreciated, also, that thecasings of these valves may be integrally fashioned as well withoutdeviating from any of the inventive concepts hereof. During normaloperation the spring 148 is stressed to permit the pressure in conduit139 to cause the ball 142 to assume a position out of engagement withthe valve seats 143 and 144 and thereby allow fluid from pump 28 to flowinto bore 41. When this area is filled and no additional make-up fluidis required the excess will bleed off to the reservoir through thecombination bleed and relief valve 131. However, in the event a surgeoccurs in the main hydraulic circuit being supplied by pump 28 theexcess pressure thus created will cause ball 142 to engage valve seat143 and prevent this excess surge pressure being transmitted into bore41. On the other hand, when a surge occurs in bore 41 ball 142 engagesvalve seat 144 and closes off conduit 139 to this excess surge pressure.Also, when the pressure in the charging circuit 139 falls below normal,ball 142 will seat against valve seat 144 and thus prevent loss of fluidfrom the closed circuit embracing bore 41. Such pressure decrease willalso permit relief valve 131 to close and stop fluid bleeding until thecharge pressure has returned to normal. Any loss of fluid in flexibleconduit 35, conduit 36 and the opposite end of bore 41 can be made up bymomentarily opening the by-pass valve 57. This arrangement, it will beappreciated, permits the proposed hydraulic draft sensing mechanismcircuit to be tied into the main fluid charging circuit of a vehiclewithout requiring the use of a separate fluid pressure supply for thedraft sensing circuit. If desired however, a separate fluid pressuresupply might be provided for said draft sensing circuit in which casethe valve 137 would be unnecessary and could be replaced with aconventional unidirectional type of check valve that would permit onlythe inflow of fluid to the draft signalling valve 40.

In FIGURES 67 there is illustrated a modified application of theproposed implement depth control mechanism. The modification therein isdirected to the environmental application illustrated and isparticularly related to the adaptation of the proposed control mechanismto a different form of earth-working implement and to the trail-behindhitch mechanism employed for attaching implements of that particulartype to its associated vehicle. In the modification, parts and elementsidentical to those of the initially described preferred form, shown inFIGURES l-5, have been referenced with the same reference numeralsemployed therewith, while comparable parts or components which althoughsimilar are not identical are referenced generally with similarreference numerals, whenever feasible, but in the 200 series ofnumerals.

In the modified arrangement the tractor vehicle 10 includes a rear axleand differential housing frame portion 11 to which is aflixed atopposite sides thereof, by suitable means such as the bolts 213, aU-shaped fixed drawbar 212. Apertures 212a spaced along the transverseportion of said drawbar are provided to accommodate the pin portion 215aof a universal pivotal connection 215 and said pin may be retained inposition by suitable link pin means such as shown at 215k. A draft linkassembly 14 has a forward link portion 14a that has one end thereofattached to the fixed drawbar 212 by means of the universal pivotalconnection 215 while the opposite end of said link portion is fixedlysecured to the casing of an auxiliary cylinder 32, and a rear linkportion 14b is connected at one end to a piston 33 slidably operativewithin cylinder 32 while the opposite end of said portion is pivotallyconnected at 14c to a tool bar frame indicated in its entirety at 218.It will be understood, of course, that the latter connection could be ofthe universal type if desired without deviating from any of theteachings of the present invention. The universal pivotal connection 215is arranged to permit full pivotal movement of the draft link 14 in ahorizontal plane and incidental movement in a vertical plane, while thepivotal connection 14c permits full vertical movement of the tool barframe 218 relative to said draft link and, when said latter con- 9nection is of the universal variety, incidental movement in a horizontalplane.

Suitably attached, as by the detachable connecting or clamping meansindicated generally at 2 19, to and depending from the frame 218 are aplurality of transversely spaced-apart subsoiler implements showngenerally by reference numeral 220. A transversely extending tubularrockshaft member 222 is journaled at opposite ends thereof by suitablemeans such as the journal brackets 222a (only one of which is shown)mounted on the frame 218 and attached thereto by bolt means 22%. Afiixedto and extending from the rockshaft 222 are a pair (only one of whichappears) of transversely spaced wheel-carrying lift crank arm members223 each of which rotatably mounts a support Wheel 223a A crank member224 mounted by suitable afiixing means on rockshaft 222 extends upwardlytherefrom and is pivotally connected by the pivotal clevis meansindicated at 2 24:: to the outwardly projecting end of the lift cylinderconnecting rod 27, which as previously described, is connected to thepiston slidably mounted in the lift cylinder that comprises thehydraulic actuator motor which is actuable for rocking shaft 222 andthereby raising and lowering the associated subsoiler implements 220.

The hydraulic actuator motor, as previously men tioned, along with theactuator control valve therefor are included in the unit assemblyindicated generally at 130 and which is connected by the flexibleconduits 29 and 30 to the hydraulic pump indicated at 28. The draftignalling control valve mechanism along with the sensitivity adjustingand motion-transmitting camming means plus the appropriate controlstherefor are included, as previously described, in the shell-likehousing or support structure, indicated by the reference numeral 75, andis communicatively connected to the auxiliary cylinder 32 by way of theflexible high-pressure conduits 35 and 36. A plate-like bracket orplatform support member 225 carried by the tool bar frame 218, andsecured thereto by suitable fastening means such as the bolts and nutsindicated at 225a, may be provided to supportably mount the units 75 and130 thereon while any well known mounting means such as the brackets andbolts indicated at 2251; may be utilized to afiix said units securelythereon.

As previously described the actuator control rod 113 extending outwardlyfrom the unit 75 pivotally connects with the walking beam link member125 which, in turn,

pivotally connects with the plunger 129 of the actuator valve and withthe lift cylinder connecting rod 27.

Operation In operation, manual movement of the control handle 107 ineither direction will, under certain positions of cam member 89, incur acorresponding movement of the piston 26 of the hydraulic motor or ramcylinder 25. For instance, a forward or upward movement of the upper endof control handle 107 will, acting through the cam track 105 and camfollower pin 104, cause vertical down- 'ward movement of guide rod 101and its'attached cam support frame 95 which carries with it the cammember 89. Since the cam 89 is restricted against rearward lateralmovement by the spring 51, of draft signalling valve 40, and when thecam member 89 is in the draft control operating range thereof and henceat an elevation such as to permit the ridge 111 of cam track 110 toclose the gap therebetween and then engage follower roller 117 this willeffect forward movement of the actuator control rod 113 which thereuponcauses counterclockwise swinging of the walking beam 125 about the thenfixed pivot 126 and endwise movement of the actuator control valve spoolor plunger element 129 forwardly or to the right as viewed in FIGURE 2.This forward movement of said control valve element will cause fluid tobe introduced into the right end of cylinder 25, in a manner readilyunderstood from a perusal of the operation of said referenced U.S.patent, whereupon the piston 26 is moved rearwardly to raise or lift theattached implement and carrying with it the upper end of walking beam125 and in this manner causing said walking beam link to pivot about itsthen fixed pivot 124 until the actuator control valve spool or plungeris moved rearwardly and returned to its initial or neutral position.

Movement of the control handle 107 counterclockwise, under similarconditions and with cam member 8? in its draft-control range, will causea vertical upward movement of guide rod 101 and its associated camsupport frame together with said cam member. Since cam member 89 isrestricted against free lateral movement by spring 46, of signallingvalve 40, and with said cam member at an elevation to permit suchengagement, and since cam track 90 inclines rearwardly said cam memberwill move laterally rearwardly on rollers 94 as it is elevated,whereupon ridge 112 of cam track after closing any gap between saidridge and its engageable follower roller 117 will effect a rearwardmovement of the actuator rod 113 which thereupon causes a clockwiseswinging of the walking beam about the then fixed pivot 126 and endwisemovement of the control valve spool control element 129 rearwardly or tothe left. as viewed in FIGURE 2. This rearward movement of the valvecontrol element will cause fluid to be introduced into the left end ofthe cylinder 25 whereby the piston 26 is moved forwardly to lower ordrop the implement and carrying with it the upper end of walking beamlink 125 and in this manner causing said walking beam link to pivotabout its then fixed pivot 124 until the control valve spool or plungeris moved forwardly and returned to its initial or neutral position.

Normally the by-pass or tilt valve 57 is positionably conditioned forrestricting free flow of fluid therethrough with the components thereofbeing disposed substantially as illustrated in FIGURE 2. However, in theevent it becomes desirable to utilize this advantageous and simplefeature of the invention for adjusting the tilt or angular displacementof the implement, as illustrated in FIG- URES 1 and 2, the controlhandie 81 is manually manipulated to move the plunger rod 55 downwardlyagainst the reaction of spring 71 thereby effecting a positioning ofaperture 66, in piston 64, into registering alignment with port openings60 and 61 so as to permit free fluid communication, by way of conduits62, 63 between opposite sides of cylinder 32 in the upper link 14. Underthis condition said upper link may be readily adjusted by manualmovement thereof to any preselected length required to provide thedesire implement tilt. When the desired length for link 14 has beenattained control handle 81 is returned to its initial position whereuponspring 71 reacts to raise piston 64 to its original position and in sodoing interrupts fluid communication between ports 60 and 61, thuscausing the elements of link 14 to tend to function as a substantiallyrigid non-yielding member instead of as a telescoping structure uponapplication thereto of tension and compression forces by the attachedimplement.

Assume now that the implement has been lowered to its desired Workingdepth in the soil whereupon the draft thereof will be balanced againstthe difference in forces set-up thereby between opposite faces of thepiston 42, in valve 40, and said implement will continue to function atthe selected depth so long as the draft load thereon does not vary. Uponencountering a variation in soil density or some other circumstancewhich causes an increase in draft load, the implement will tend to swingupwardly either about the pivots 13 or about the pivotal connections ofmast 17 with the lower draft links 12. This action produces a forwardmovement of the rear link portion 141) which thereupon tends totelescopingly compress upper link 14. This results in an increasedcompressive force in said upper link which thereupon tends to urgepiston 33, of cylinder 32, forwardly or to the right as viewed herein,thus forcing fluid from the right end of said cylinder through conduits35, 37 into the left end of bore 41, of valve 46, where such fluidreacts against the left face of piston 42 endeavoring to overcome thereactive resistance thereto of spring 46 and the reaction of the fluidon the opposite face of piston 42. However, since the pressure inconduits 36, 38 is simultaneously reduced upon an inward movement ofpiston 33 the difference in pressure between opposite ends of saidcylinder thus becomes effective to accomplish movement forwardly, or tothe right, of piston 42 within the bore 41 and likewise of its attachedplunger member 48.

Since the effective diameter or exposed face or pressure area of piston33 is much greater than the corresponding face of piston 42 this resultsin an increased mechanical advantage whereby a very small lateralmovement of piston 33 produces an appreciable correlated lateralmovement of piston 42. This feature is particularly advantageous sinceit permits a very small as well as a large change in draft to be readilysensed and registered and subsequently reflected by way of a muchgreater lateral movement in the signal transmitting elements of thedevice, thus the device is made materially more sensitive andsusceptible for sensing and correcting for small as wall as largevariations in the draft load. Inasmuch as the roller 86 and pin 88 onthe end of the plunger 48 are in contacting engagement with oppositefaces of track 90, of cam member 39, and vertical movement of said cammember restrained by the frictional holding means of handle 107, anylateral movement of plunger 48 will incur a comparable movement of saidcam member. When the cam member 8% has traveled a horizontal distancesufficient to close any gap between follower roller 117 and ridge 111,of cam track 110, said roller will pick-up the signalling movement beingtransmitted through cam member 89 and transmit it by way of actuatorcontrol rod 113 to the actuator control valve 31. In the presentinstance, this will cause walking beam link member 125 to swingcounterclockwise about pivot 126 thereby effecting a lifting or raisingof the implement which thereupon causes a decrease in the draft on saidimplement.

In a similar manner when a condition is encountered which results in adecrease in draft load the implement tends to swing downwardly or rotatecounterclockwise about its pivotal connections. This produces a rearwardmovement of the rear link portion 14b which thereupon tends to elongateor stretch the upper link 14 and incident thereto to place said link intension. This action tends to urge piston 33, of cylinder 32,rearwardly, or to the left as viewed herein, thus forcing fluid from theleft end thereof through conduits 36, 38 and into the right end of bore41, of valve 40, where such fluid reacts against the right face ofpiston 42 endeavoring to overcome the reactive resistance thereto ofspring 51 and the reaction of the fluid on the opposite face of saidpiston. Since the pressure in conduits 35, 37 is concomitantly reducedupon such movement of piston 33 the difference in pressure betweenopposite ends of said cylinder thus becomes effective to accomplishmovement rearwardly of piston 42 and its attached plunger member 48.Since roller 86 and pin 88 on plunger 48 are in engaging contact withopposite sides of track 90, of cam member 89, which is restrainedagainst vertical movement, any lateral movement of plunger 48 will incura similar movement of said cam member. With cam member 89 in the draftcontrol range thereof, when the gap between roller 117 and ridge 112, ofcam track 110, has been closed said roller will then pick-up thesignalling movement being transmitted through cam member 89 and transmitit by way of actuator control rod 113 to the actuator control valve 31.In this instance, such movement will cause walking beam 125 to swingclockwise about pivot 126 thereby effecting a lowering or dropping ofthe implement 12 which thereupon reestablishes the desired draft load onsaid implement.

The operation of the modified arrangement illustrated in FIGURES 6 and 7is generally similar to the embodiment shown in FIGURES l5. Asheretofore explained in detail, in describing the operation of thepreferred form illustrated in FIGURES 1-5, the control handle 107 may berotated to cause actuation of the lift cylinder for rocking rockshaftwheels 223a and in that way conversely lower and raise the earth-workingimplement 220 to vary the depth thereof in the ground. Now assume, asbefore, that the implement 220 has been lowered to its desired workingdepth in the soil and the draft load thereon balanced against thedifference in forces set up thereby between opposite faces of the pistonin the draft signalling valve contained within the unitary assembly 75,whereupon said implement will continue functioning at the selected depthuntil encountering a variation in draft load thereon. Upon encounteringan increase is draft load, the implement while tending to swing or pivotabout its pivotal connection 140 will at the same time tend to elongatethe draft link 14 by producing a rearward movement of the rear linkportion 1415 thereof. Since link portion 14b is constrained for movementwith piston 33 a rearward movement of said piston operates to forcefluid from the left end of auxiliary cylinder 32 out through conduit 35'and into one end of the draft signalling valve contained in unit where,as previously related, this produces an increase in pressure in one endof the valve and causes a forward movement of the plunger thereof. Thislatter movement, in turn, produces a forward movement of actuatorcontrol rod 113 which transmits such movement signal by way of theinterconnected spool plunger 129 to the actuator control valve in unit130 which then responds to actuate the hydraulic lift cylinder and tolower the support wheels 223a and thereby raise the implement so as todecrease the draft load thereon. It will be apparent from the above thatin the modified arrangement an increase in draft load produces arearward movement of piston 32 in auxiliary cylinder 33 whereas in theother preferred embodiment such increase produces a forward movementthereof, but this is readily compensated for by reversing the conduitconnections 35 and 36 between the cylinder and unit 75 without deviatingfrom any fundamental teachings of the invention.

Next assume a condition which results in a decrease in draft load. Inthis case the rearward urging of the implement is decreased whereuponthe fluid pressure in the left end of auxiliary cylnder 32 is able toreact and effect a forward movement of piston 3-3 and hence a shorteningof draft link 14. This movement produces an outflow of fluid from theforward end of said auxiliary cylinder by way of conduit 36 into theforward end of the draft signalling valve which thereupon produces anlncrease in pressure in this end of said valve and such increase causesa rearward movement of the plunger thereof. Said latter movement, inturn, causes a rearward movement of actuator control rod 113 whichtransmits such movement signal by way of the interconnected spoolplunger 129 to the actuator control valve in unit 13f? which thenresponds to actuate the hydraulic lift cylinder and to raise the supportwheels 223a and thereby drop the implement so as to re-establish thedesired draft load on said implement.

It will be seen from the foregoing that the proposed mechanism is highlyeffective for maintaining a substantially constant draft load on theimplement, and because of the mechanical advantage developed thereinprovides an apparatus that is highly sensitive for registering andcorrecting for implement draft variations of minimum as well as maximummagnitudes. It will also be appreciated that a very simple means hasbeen incorporated in the mechanism for adjusting the length of the upper13 link of the hitch and concomitant therewith altering the angle ortilt of an implement in the soil.

It will be noted that the opposite ridges 11:1, 112 of cam track 119diverge from one another so that the lateral dimension of cam track 11%changes considerably from one end to the other thereof, and that onlyadjacent the upper end thereof does the roller 117 contactingly engageboth said ridges at the same time. The purpose of this arrangement is toprovide for variation in the degree of sensitivity or magnitude of draftload change required to effect response of said mechanism. For instance,when the cam track 110 is in such position that both sides thereofsimultaneously contact roller 117 any lateral movement of cam member 89will immediately be transmitted to the control valve 31 to effect anappropriate correction in the elevation of the attached implement.However, there are circumstances when, because of frequentirregularities of ground contours or frequent changes in soil density orother similar conditions, it becomes desirable to provide variablesensitivity or varying degrees of magnitude of draft load changetoeffect response of the device in order to reduce the frequency ofcorrections being effected. This is readily accomplished in the presentinvention merely by rotating the control handle 107 and thereby changingthe elevation of the cam member 89. This has the effect of modifying thepoint of engagement of the roller 117 with the appropriate ridge of camtrack 1'10 and thereby providing in effect a lost-motion connectiontherebetween. By decreasing the gap or spacing between the roller 1 17and its respective engaging ridge member the sensitivity or magnitude ofdraft load change required to effect response is decreased, and,conversely, by increasing this gap or spacing the sensitivity ormagnitude of draft load change required to effect response is increased.

Referring to FIGURE 2 of the drawings, it will be seen that anintermediate portion of the right hand side of cam member 89 is devoidof any cam or ridge member that is engageable with roller 117. This istermed the No Effect zone or null area and when the cam member 89 is 50positioned that roller 117 rests in this No Effect zone any lateralmovement of said cam member will produce no comparable movement of saidroller, hence the control valve 31 will not be operatively responsive tosuch movements. The friction bearing shoe or block 120 creates afriction on actuator rod 113 which resists axial movement of said rodwhich is such that it can be overcome by movement of cam member 89 butcannot be overcome by movement of the walking beam member 125. This, ofcourse, is particularly useful when the roller 117 is disposed in the NoEffect zone of cam member 89.

The cam track 109 provides a manual over-ride means for lowering theimplement. When the cam member 89 has been raised to a position suchthat the roller 117 is disposed in the No Effect zone of said cam memberthe vertical alignment thereof will be such that the lower edge of ridge112 of track 110 may, under some circumstances of draft load or the lastused lift position, interfere with a lowering of the cam member 89 whenit is desired to reposition said roller within the draft control rangeof cam track 110. Hence, in order to accomplish this the cam member 89is first raised by control handle 107 until roller 117 engages track 109and moves said roller leftwardly a distance sufficient to permit itsre-entry into cam track 110 when said cam member is subsequently loweredby manipulation of said control handle.

Although only preferred embodiments, which show the invention utilizedin association with an upper link element of a hitch linkage, and with adraw-bar type single point linkage have been illustrated and describedherein, it will be appreciated that it is not limited to suchapplication since it may readily be applied to lower link elements aswell as to other draw-bar types of hitch installations with equalfacility without deviating from any teachings of the inventive conceptshereof.

Variants in individual components of the mechanism disclosed willreadily occur to skilled designers in the field. Accordingly, eventhough a particular embodiment and application of the invention has beenshown and described in some detail, there is no intention to therebylimit the invention to such specific form or the particular employmentshere indicated. On the contrary, the intention is to cover allmodifications and alternative arrangements falling within the spirit andscope of the present invention as expressed in the appended claims.

What is claimed is:

1. In a tractor having implement-attaching mechanism including aplurality of hitch links trailingly pivoted on the rear portion of thetractor and having means at their trailing ends for pivotal attachmentat vertically spaced points to an earth-working implement and stressedin direct relationship to the draft load thereon, hydraulic actuatormeans mounted on the tractor and connected to said links for raising andlowering an attached implement, and actuator control valve meansactuable for controlling the operation of said actuator means, thecombination comprising: draft-sensing means including hydraulic motormeans telescopingly interposed exteriorly of the tractor in at least oneof said links; draft-signalling means including a hydraulic displacementdevice supportably carried by the tractor; conduit means including asupply of hydraulic fluid therein communicatively interconnecting saidhydraulic motor means and said hydraulic displacement device; saidhydraulic motor .means being telescopingly operative for creatingpressure differentials proportional to the draft load between oppositeends of said hydraulic motor means attendant draft-produced changes instress in said links; said hy draulic displacement device having meanstherein variably positionable responsive to said pressure differentials;and movement-transmitting means interconnected between saiddraft-signalling means and said actuator control valve means andoperatively responsive to movements of said variably positionable meansfor actuating said actuator control valve means to effect an adjustmentof the depth of the implement in the ground and thereby to maintain asubstantially constant draft thereon.

2. In a tractor having implement-attaching mechanism including upper andlower hitch links trailingly pivoted at vertically spaced points on therear portion of the tractor and having means at their trailing ends forpivotal attachment at vertically spaced points to an earthworkingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement, andactuator control valve means actuable for controlling the operation ofsaid actuator means, the combination comprising: draftsensing meansincluding hydraulic motor means telescopingly interposed exteriorly ofthe tractor in one of said links; draft-signalling means including ahydraulic displacement device supportably carried by the tractor;conduit means including a supply of hydraulic fluid thereincommunicatively interconnecting said hydraulic motor means and saidhydraulic displacement device; said hydraulic motor means beingtelescopingly operative for creating pressure differentials proportionalto the draft load between opposite ends of said hydraulic motor meansattendant draft-produced changes in stress in the link in which the sameis interposed; said hydraulic displacement device having means thereinvariably positionable responsive to said pressure differentials;movement-transmitting means interposed between said draftsignallingmeans and said actuator control valve means and operatively responsiveto movements of said variably positionable means for actuating saidactuator control valve means to selectively effect a raising andlowering of an attached implement and thereby to maintain asubstantially constant draft thereon; and means including a by-passvalve communicatively connected between opposite ends of said hydraulicmotor means and having said valve operable to establish free fiuidcommunication between the opposite ends of said hydraulic motor meanswhereby the effective length of the link in which said hydraulic motormeans is interposed may be varied for effecting rocking of an attachedimplement fore and aft incident to such change in link length. I

3,. The structure defined in claim 2 further characterized in thatmanually operable control means are provided for operating said by-passvalve and moving same from a position restricting free flow of hydraulicfluid between opposite ends of said hydraulic motor means to a positionpermitting free flow therebetween whereby to effect a change in theangular position of engagement of the implement with the earth beingworked. i

4. The structure defined in claim 3 and further characterized in thatthe means including said by-pass valve is fashioned as an individualunit and mounted on and securedly afiixed to said hydraulic displacementdevice.

5. In a tractor having implement attaching rnechanism including an upperhitch link and a pair of lower hitch links trailingly pivoted atvertically spaced points on the rear portion of the tractor and havingmeans at their trailing ends for pivotal attachment at vertically spacedpoints to an earth-working implement, hydraulic actuator means connectedto said links for raising and lowering an attached implement, andactuator control valve means actuable for controlling the operation ofsaid actuator means, the combination comprising: means includinghydraulic motor means interposed in said upper link exteriorly of thetractor and being telescopingly operable for varying the effectivelength of said' link; draft-signalling means including a hydraulicdisplacement device supportably carried by the tractor; conduit meansincluding a supply of hydraulic fluid therein communicativelyinterconnecting said hydraulic motor means and said hydraulicdisplacement device in a closed circuit; said hydraulic motor meansbeing telescopingly operative for creating pressure differentialsproportional to the draft load between opposite ends of said hydraulicmotor means attendant draft-produced variations in stress in said upperlink; said hydraulic displacement device having means therein variablypositionable responsive to said pressure differentials;motion-transmittingmeans connected to said hydraulic displacement deviceand engageable with said actuator control valve means and operativelyresponsive for transmitting movements of said variably positionableelement to said actuator control valve means for selectively actuatingthe same to effect a raising and lowering of an attached implement tothereby maintain a substantially constant draft on the implement; andmeans including a by-pass valve communicatively connected betweenopposite ends of said hydraulic motor means and operable to permit freefluid communication therebetween whereby the effective length of saidupper link may be varied for effecting rocking of the implement fore andaft.

6. In a tractor having implement attaching mechanism including upper andlower hitch links trailingly pivoted at vertically spaced points on therear portion of the tractor and having means at their trailing ends forpivotal attachment at vertically spaced points to an earth-workingimplement, hydraulic actuator means connected to said links foreffecting vertical movement of an attached implement, and actuatorcontrol valve means actuable for controlling the operation of saidactuator means, the combination comprising: hydraulic motor meansinterposed in at least one of said links exteriorly of the tractor andexpandible and contractible for varying the effective length of said oneof said links; hydraulic draft signalling means supportably carried bythe tractor; conduit means including a supply of hydraulic fluid thereincommunicatively interconnecting said hydraulic motor means and saidhydraulic draft signalling means; said hydraulic motor beingtelescopingly operative for creating pressure differentials proportionalto the draft load between opposite ends of said hydraulic motor meansattendant draft-produced variations in stress in the link in which thesame is interposed; said hydraulic draft-signalling means including ahydraulic displacement device having an element therein variablypositionable responsive to said pressure differentials, and a by-passvalve interconnected with said conduit means and having fluidcommunication with opposite ends of said hydraulic motor means, andmeans for manually operating said by-passvalve to permit free fluidcommunication between opposite ends of said hydraulic motor meanswhereby the effective length of the link in which said latter meansisinterposed may be changed to effect a change in the angular position ofengagement of an attached implement with the earth being worked; andmotion-transmitting means connected to said hydraulic displacementdevice and engageable with said actuator control valve means andoperatively responsive for translating movements of said variablypositionable element to said actuator control valve means for actuatingthe same to effect an adjustment in the depth of an attached implementin the ground to thereby maintain a substantially constant draft on animplement.

7. In a tractor having implement-attaching mechanism including upper andlower hitch links trailingly pivoted at vertically spaced points on therear portion of the tractor and having means at their trailing ends forpivotal attachment at vertically spaced points to an earth-workingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement, andactuator control valve means actuable for controlling the operation ofsaid actuator means, the combination comprising: means including anexpandable and contractible hydraulic device interposedin one of saidlinks; draft-signalling-means including a hydraulic displacement devicesupportably carried by the tractor; conduit means including a supply ofhydraulic fluid therewith communicatively interconnecting said hydraulicdevice and said hydraulic displacement device; said hydraulic devicebeing operative upon expansion and contraction for creating pressuredifferentials between opposite ends thereof that reflect draft-producedchanges in stress in said one of said links; said hydraulic displacementdevice having an element therein variably positionable responsive tosaid pressure differentials; movement-transmitting means interposedbetween said draft-signalling means and said actuator control valvemeans and operative responsive to movements of said variablypositionable element for actuating said actuator control valve means toeffect through selective operation of said hydraulic actuator means araising and lowering of an attached implement to thereby maintain asubstantially constant draft on the implement; said movementtransmittingmeans including manually adjustable means operable to vary thesensitivity of response thereof for transmitting the movements of thehydraulic displacement device to said actuator control valve means.

8. The invention according to' claim 7 further characterized in thatsaid movement-transmitting means includes lost-motion connecting meansand means for adjusting the latter whereby the etfective length of saidmovement-transmitting means is modified to vary themovement-transmitting sensitivity thereof.

9. The invention according to claim 7 further characterized in that saidmovement-transmitting means includes a cam means connected at one edgethereof to said variablepositionable element for movement therewith andhaving proximate an oppositeedge thereof a cam track with opposite sidesof said track diverging from one another and having follower means withone end thereof positionable in an rengageable with said diverging camtrack and having an opposite end of said follower means operativelyconnected to said actuator control valve means, and further in that saidcam means is manually adjustable to vary the point of engagement of saidfollower means with said diverging cam track whereby to vary theeffective length and movement-transmitting sensitivity of saidmovement-transmitting means.

10. In a tractor having implement attaching mechanism including upperand lower hitch links trailingly pivoted at vertically spaced points onthe rear portion of the tractor and having means at their trailing endsfor pivotal attachment at vertically spaced points to an earthworkingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement, andactuator control valve means actuable for controlling the operation ofsaid actuator means, the combination comprising: hydraulic motor meansinterposed in at least one of said links exteriorly of the tractor andexpandible and contractible for creating pressure differentialsproportional to the draft load between opposite ends theerof in responseto changes in stress in the link in which the same is interposed as aresult of variations in draft loads imposed on the tractor by anattached implement; hydraulic displacement means mounted on the tractorand including means therein variably positionable in accordance withsaid pressure differentials created between opposite ends of saidhydraulic motor means; conduit means including a supply of hydraulicfluid therein communicatively interconnecting said hydraulic motor meansand said hydraulic displacement device; motion-transmitting meansinterposed between said hydraulic displacement device and said actuatorcontrol valve means and operatively responsive to the movements of saidvariably positionable means for actuating said actuator control valvemeans to effect through selective operation of said hydraulic actuatormeans a raising and lowering of an attached implement to therebymaintain a substantially constant draft on the implement.

ill. The invention according to claim further characterized in that saidmotion-transmitting means includes lost motion means and means foradjusting said latter means and wherein said lost motion means ispositionably adjustable to a position such that no movements of saidvariably positionable means are transmitted to said control valve means.

12. The invention according to claim 10 further characterized in thatsaid motion-transmitting means includes manually adjustable meansoperative to eflect actuation of said actuator control valve means tocause a raising and lowering of an attached implement independent ofmovements of the variably positionable means of said hydraulicdisplacement means.

13. In a tractor having implement attaching mechanism including upperand lower hitch links trailingly pivoted at vertically spaced points onthe rear portion of the tractor and having means at their trailing endsfor pivotal attachment at vertically spaced points to an earthworkingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement, andactuator control valve means actuable for controlling the operation ofsaid actuator means, the combination comprising: means including anauxiliary cylinder and piston slidable therewithin interposed in one ofsaid links and operative for creating pressure di'lferentials betweenopposite ends of the cylinder in response to changes in stress imposedin said one of said links as a result of variations in draft loads on anattached implement; a hydraulic displacement device supportably carriedby the tractor and fashioned to provide a bore therein and having apiston variably positionable within said bore, and having a plungerportion of said latter piston extending outwardly of said device;conduit means including a supply of hydraulic fluid thereincommunicatively interconnecting opposite ends of said auxiliary cylinderand said bore; said displacement device piston and plunger beingvariably positionable in said :bore in accordance with the pressuredifferentials created between opposite ends of said auxiliary cylinder;motion-transmitting means connected with the outwardly extending plungerportion of said displacement device piston and with said actuatorcontrol valve means and operative for transmitting the variablypositionable movements of said latter piston and plunger within saidbore to said actuator control valve means for actuating said lattermeans to effect through operation of said hydraulic actuator means araising and lowering of an attached implement to thereby maintain asubstantially constant draft on the implement.

14. The invention according to claim 13 further characterized in thatthe effective face area of the auxiliary piston exposed to hydraulicpressure is substantially greater than the effective exposed face areaof the variably positionable piston whereby small increments of movementof the auxiliary piston within the auxiliary cylinder result insubstantially greater movements of the piston within the bore of saidhydraulic displacement device.

15. In a tractor having implement attaching mechanism including upperand lower hitch links trailingly pivoted at vertically spaced points onthe rear portion of the tractor and having means at their trailing endsfor pivotal attachment at vertically spaced points to an earth-workingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement, andactuator control valve means ac tuable for controlling the operation ofsaid actuator means, the combination comprising: means including anauxiliary cylinder and piston slidable therewithin interposed in one ofsaid links and operative for creating pressure differentials betweenopposite ends of the cylinder in response to changes in stress imposedin said one of said links as a result of variations in draft loads on anattached implement; a hydraulic displacement device supportably carriedby the tractor and fashioned to provide a bore therein and having apiston variably positionable within said bore, and having a plungerportion of said latter piston extending outwardly of said device;conduit means including a supply of hydraulic fluid thereincommunicatively interconnecting opposite ends of said auxiliary cylinderand said bore; said displacement device piston and plunger beingvariably positionable in said bore in accordance with the pressuredifferentials created between opposite ends of said auxiliary cylinder;motion-transmitting means interposed between said hydraulic displacementdevice and said actuator control valve means and including manuallyadjustable cam means, and means interconnecting the outwardly extendingplunger portion of said displacement device with said cam means, linkmeans connected at one thereof to said actuator control valve means andhaving another end thereof disposed for contacting engagement with saidcam means, said cam means being adjustable to a plurality of positionsin certain of which positions said cam means is effective fortransmitting movements of the variably positionable piston of saidhydraulic device to said actuator control valve means for actuating saidlatter means to efifect a raising and lowering of an attached implementto thereby maintain a substantially constant draft on the implement andin certain other positions thereof said cam means is effective forinterrupting the transmission of movements between said variablypositionable piston and said actuator control valve means.

16. In a tractor having implement-attaching mechanism including upperand lower hitch links trailingly pivoted at vertically spaced points onthe rear portion of the tractor and having means at their trailing endsfor pivotal attachment at vertically spaced points to an earth-workingimplement, hydraulic actuator means mounted on the tractor and connectedto said links for raising and lowering an attached implement andincluding a source of fluid pressure and a reservoir having a supply offluid therein, and actuator control valve means actuable for controllingthe operation of said actuator means, the combination comprising: meansincluding an auxiliary piston and cylinder interposed in one of saidlinks and being operable for varying the effective length of the link inwhich same is interposed; hydraulic displacement means supportablycarried by the tractor; conduit means including a supply of hydraulicfluid therein communicatively interconnecting said auxiliary cylinderand hydraulic displacement means in a closed circuit; said auxiliarypiston being operatively slidable within said auxiliary cylinder forcreating pressure differentials between opposite ends of said cylinderattendant draft-produced variations in stress in said one of said links;said hydraulic displacement means having means therein variablypositionable responsive to said pressure differentials;motion-transmitting means connected to said hydraulic displacement meansand engageable with said actuator control valve means and operativelyresponsive for transmitting movements of said variably positionablemeans to said actuator control valve means for actuating the same toeffect a raising and lowering of an attached implement to therebymaintain a substantially constant draft on the implement; meansincluding a by-pass valve communicatively connected between oppositeends of said auxiliary cylinder and operable to permit free fluidcommunication therebetween whereby the effective length of said one ofsaid links may be varied for effecting a rocking of the implement foreand aft; fluid make-up and pressure relief means including a first valvemeans and a second valve means and means communicatively connecting saidfirst valve means with said hydraulic displacement means and said sourceof fluid pressure and said second valve means with said hydraulicdisplacement means and said reservoir, said first valve means includingvalving means selectively conditionable in a first position forpermitting transmission of fluid under pressure from said fluid pressuresource to said hydraulic displacement means, and in a second positionfor interrupting transmission of fluid from said fluid pressure sourceto said hydraulic displacement means attendant an appreciable increasein the pressure of said fluid pressure source, and in a third positionfor interrupting transmission of fluid from said hydraulic displacementmeans to said fluid pressure source attendant an appreciable increase inpressure in said displacement means, said second valve means includingvalving means biased toward a closed position but operative attendantpressures normally encountered in said hydraulic displacement means topermit bleed therethrough to said reservoir of fluid excess to therequirements of said hydraulic displacement means and being operative toa closed position upon a drop of pressure in said hydraulic displacementmeans below a preselected minimum pressure.

17. The invention according to claim 16 further characterized in thatthe valving means of said first valve means includes a ball valveelement and a pair of longitudinally spaced and oppositely facing valveseats selectively engageable by said ball valve element to interrupt theflow of fluid therethrough first in one direction and then in anotherdirection, and further in that said valving means includes means biasingsaid ball valve element into position intermediate said valve seats inopposition to incoming fluid pressure whereupon fluid may be transmittedtherethrough from said fluid pressure source.

References Cited by the Examiner UNITED STATES PATENTS 2,397,270 3/1946Kelly 54.5 X 2,455,727 12/1948 Bunting 1728 2,750,862 6/1956 Garmager172-7 2,754,742 7/1956 Altgelt 172-9 2,782,703 2/1957 Chambers et al.1727 2,981,341 4/1961 Dilworth 172-2 3,002,571 10/1961 Kersey et a1.172-9 ABRAHAM G. STONE, Primary Examiner.

FRANCIS B. HENRY, Assistant Examiner.

1. IN A TRACTOR HAVING IMPLEMENT-ATTACHING MECHANISM INCLUDING APLURALITY OF HITCH LINKS TRAILINGLY PIVOTED ON THE REAR PORTION OF THETRACTOR AND HAVING MEANS AT THEIR TRAILING ENDS FOR PIVOTAL ATTACHMENTAT VERTICALLY SPACED POINTS TO AN EARTH-WORKING IMPLEMENT AND STRESSEDIN DIRECT RELATIONSHIP TO THE DRAFT LOAD THEREON, HYDRAULIC ACTUATORMEANS MOUNTED ON THE TRACTOR AND CONNECTED TO SAID LINKS FOR RAISING ANDLOWERING AN ATTACHED IMPLEMENT, AND ACTUATOR CONTROL VALVE MEANSACTUABLE FOR CONTROLLING THE OPERATION OF SAID ACTUATOR MEANS, THECOMBINATION COMPRISING: DRAFT-SENSING MEANS INCLUDING HYDRAULIC MOTORMEANS TELECOPINGLY INTERPOSED EXTERIORLY OF THE TRACTOR IN AT LEAST ONEOF SAID LINKS; DRAFT-SIGNALLING MEANS INCLUDING A HYDRAULIC DISPLACEMENTDEVICE SUPPORTABLY CARRIED BY THE TRACTOR; CONDUIT MEANS INCLUDING ASUPPLY OF HYDRAULIC FLUID THEREIN COMMUNICATIVELY INTERCONNECTING SAIDHYDRAULIC MOTOR MEANS AND SAID HYDRAULIC DISPLACEMENT DEVICE; SAIDHYDRAULIC MOTOR MEANS BEING TELESCOPINGLY OPERATIVE FOR CREATINGPRESSURE DIFFERENTIALS PROPORTIONAL TO THE DRAFT LOAD BETWEEN OPPOSITEENDS OF SAID HYDRAULIC MOTOR MEANS ATTENDANT DRAFT-PRODUCED CHANGES INSTRESS IN SAID LINKS; SAID HYDRAULIC DISPLACEMENT DEVICE HAVING MEANSTHEREIN VARIABLY POSITIONABLE RESPONSIVE TO SAID PRESSURE DIFFERENTIALS;AND MOVEMENT-TRANSMITTING MEANS INTERCONNECTED BETWEEN SAIDDRAFT-SIGNALLING MEANS AND SAID ACTUATOR CONTROL VALVE MEANS ANDOPERATIVELY RESPONSIVE TO MOVEMENTS OF SAID VARIABLY POSITIONABLE MEANSFOR ACTUATING SAID ACTUATOR CONTROL VALVE MEANS TO EFFECT AN ADJUSTMENTOF THE DEPTH OF THE IMPLEMENT IN THE GROUND AND THEREBY TO MAINTAIN ASUBSTANTIALLY CONSTANT DRAFT THEREON.